MDF - Speaker cabinet damaged - how to properly paint

The place for discussions that don't fit into any of the above categories
Post Reply
CosmosisT
Posts: 27
Joined: Thu Mar 15, 2018 6:13 am

MDF - Speaker cabinet damaged - how to properly paint

Post by CosmosisT » Thu Mar 15, 2018 9:03 pm

How does one achieve a professional prime on MDF corner/face and make for a glossy finish?

Speaker took a nasty fall and I had to remove all the laminate and now see about patching gouges and marks throughout. Painting will be last but need a full-proof process, to turning them from rough to brand new.

I'll have pictures tomorrow really looking for tips on working with MDF repairing/painting/finishing it.

User avatar
A. Spruce
Posts: 5881
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: MDF - Speaker cabinet damaged - how to properly paint

Post by A. Spruce » Thu Mar 15, 2018 11:05 pm

As long as the MDF is not broken or swollen from moisture, you can pretty much treat it the same as wood. Fill low areas with a sandable wood filler, prime, paint.

It would be best to use an oil based primer, preferably aerosol for the smoothest possible texture. Oil based because oil will not raise the MDF fiber. Any automotive aerosol primer should suffice. Apply two coats of primer with a light sanding in between. Give another light sand before applying top coat, again, I'd use an aerosol for best results. You may or may not need to sand between top coats, depending on how well the paint lays down.
If the women don't find you handsome, they should at least find you handy.

CosmosisT
Posts: 27
Joined: Thu Mar 15, 2018 6:13 am

Re: MDF - Speaker cabinet damaged - how to properly paint

Post by CosmosisT » Fri Mar 16, 2018 6:17 am

Pardon the garden setup on the table, seedling time!

The MDF was laminated top to bottom and back. The front would appear MDF with a nice finish.

It's in great shape just gouges taken out of the body and face of the unit.

I can't get any close-ups on the damage, with this camera but these pictures should paint an idea.


The MDF is in great shape just the few nicks/scars,

To be certain, is there a type of wood filler I should be using? Will this affect the priming aspect? Will this adhere properly and do its job?

In regards to adhering, would I need to open the damage up more?

When treating the front face that's painted, would I have issues priming it?

I guess a bit of the concern is that the MDF body is unfinished whereas the face is and I'd want to prime/paint these properly but repair them in such way I don't have to worry about my finger popping filler out if I handle them needs to be strong for a cabinet.

Would it be safe to say the primer I use to hit the raw MDF can be used to hit the front when it's all patched? Not trying to remove the finish but work over-top of what you see here once patched.
Attachments
GOPR1058.JPG
GOPR1058.JPG (65.91 KiB) Viewed 425 times
GOPR1057.JPG
GOPR1057.JPG (46.66 KiB) Viewed 425 times
GOPR1056.JPG
GOPR1056.JPG (60.45 KiB) Viewed 425 times

CosmosisT
Posts: 27
Joined: Thu Mar 15, 2018 6:13 am

Re: MDF - Speaker cabinet damaged - how to properly paint

Post by CosmosisT » Fri Mar 16, 2018 7:00 am

In the second picture you can see the machined MDF with a rough painted surface in around the holes on its face high-end finish with a nasty nicks/scars.

This portion I believe 90% it's a paint.

In my mind I'd think for filling too, I'd need to cut out the marks more and maybe drill small holes this way I get better adhesion. Some of the damage is too small to can it really adhere well without me preparing first?

Any advice before I tackle would be nice, MDF is a new one for me don't touch it, don't like to but who knows that could change.

I'm definitely going to need to spray this, but need to track down a safe-to use quality product. Need to deem myself comfortable with this project.

I'm wondering if I'll need to run some paint-remove on the front face or if that'd matter at all if I could just hit it with primer and bring the whole thing a solid color once filled. Haven't had issues with paint-remover damaging wood, would MDF have the same appeal?

Thanks again :)

User avatar
A. Spruce
Posts: 5881
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: MDF - Speaker cabinet damaged - how to properly paint

Post by A. Spruce » Fri Mar 16, 2018 10:10 am

Any sandable filler should work just fine. I like Dap Plastic Wood, it is solvent based, adheres well, sands well, takes stain and paint well.

You should not need to prep any areas that need filling any more than making sure there is no loose material in or around the fill areas and that they are dust free.

It should not matter whether you're working over the painted or unpainted surfaces of the box, the materials should work just fine. I would highly recommend lightly sanding out the entire box to remove tool marks and such, those rounded corners look a bit rough to me. Also, lightly sanding the painted areas will give the primer more bite, which in turn gives the paint more bite. You will know pretty quickly whether the paint is going to react to the primer, odds are it won't, it's probably a lacquer or a polyurethane finish, both of which are pretty impervious to most other finishing products.

An aerosol primer is going to be the easiest to apply and give you the best finish. Anything cheap will do the job, it doesn't have to be name brand, it just has to state on the label that it's compatible for use on wood, most are, but check the label to be sure.

Aerosol paint will also be the easiest to use and provide the best finish. It is less important that the paint be "wood compatible" because you're shooting it over a good primer base. The one thing you do have to be aware of is that the hardeners have been removed from today's paints, so even when dry they can still be scratched easily, you may need to spray a clear coat to give you the hardness you are looking for. You can easily test this on the back of the speaker box, prime it well, paint it well, then when dry, scratch at the back with your fingernail in an inconspicuous spot, if it mars easily, clear coat it, if it doesn't you're good to go.
If the women don't find you handsome, they should at least find you handy.

CosmosisT
Posts: 27
Joined: Thu Mar 15, 2018 6:13 am

Re: MDF - Speaker cabinet damaged - how to properly paint

Post by CosmosisT » Fri Mar 16, 2018 12:49 pm

I dug out the markings more, drilled and cut out a cavity and inserted wood-filler I had on hand. If I sand this, the left over-fuzz does that get covered by the primer and sanded smooth?

Also am deciding to go with a B-I-N spray product, should be appropriate for the project and it comes in a spray edition as well!

Just curious about the sanding aspect, if the small fuzzes will impact things when I spray or if that's why we do a coat, sand and repeat.

Slowly understanding the process a bit more and gaining comfort/reassurance.4

CosmosisT
Posts: 27
Joined: Thu Mar 15, 2018 6:13 am

Re: MDF - Speaker cabinet damaged - how to properly paint

Post by CosmosisT » Fri Mar 16, 2018 1:07 pm

Picture updates, I think the fill went alright I'll likely sand down the corners remove the sharp edges clean it up but this is looking good.

Hopefully this goes down well! Not regretting digging holes out and filling deeper things are strong!
Attachments
GOPR1074.JPG
GOPR1074.JPG (43.62 KiB) Viewed 414 times
GOPR1073.JPG
GOPR1073.JPG (56.3 KiB) Viewed 414 times
GOPR1072.JPG
GOPR1072.JPG (58.3 KiB) Viewed 414 times
GOPR1071.JPG
GOPR1071.JPG (35.93 KiB) Viewed 414 times
GOPR1070.JPG
GOPR1070.JPG (50.46 KiB) Viewed 414 times

User avatar
A. Spruce
Posts: 5881
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: MDF - Speaker cabinet damaged - how to properly paint

Post by A. Spruce » Fri Mar 16, 2018 4:26 pm

What grit sandpaper are you using? The finer the grit, the less fuzz you should have, also, 220 grit between coats, the point of which is to knock down the fuzzies. Because MDF is a compressed fiber material, when it gets wet it's going to swell a bit and fuzzies (aside from your initial sanding) are going to appear. The primer also seals the surface, so by priming, sanding, priming again, you should virtually eliminate all residual fuzzies. If your first coat of paint goes on smoothly and you're not seeing any more fuzz issues, then you're done sanding, you don't necessarily need to sand between top coats.

BIN is perfectly acceptable for what you're doing.
If the women don't find you handsome, they should at least find you handy.

CosmosisT
Posts: 27
Joined: Thu Mar 15, 2018 6:13 am

Re: MDF - Speaker cabinet damaged - how to properly paint

Post by CosmosisT » Mon Mar 19, 2018 3:34 pm

I'll get pictures up soon, but I basically thus far drilled out portions of damaged MDF, and chipped away any access paint, filling voids with wood-filler. I went through it all with 120 Grit to bring down the wood fill once it had dried solid (a day or so). The sides from when laminate was removed was left quite fuzzy so during the sanding I took a chance and sanded away, upon seconds noticed the fuzzing clear right up but of course higher grit would do wonders but bring things down, lower 80 - 120 be fine just nothing rough can start taking more than you bargained for.

I was curteousy when sanding to use two different papers for the body and one for the face to prevent paint dust bleeding into the mdf (wanted clean surface).

When surfaces were roughed/sanded how I wanted at 120 grit, I sprayed a coat of BIN by zinsser. This stuff is great dried really fast but does smell quite a bit, would highly recommend doing this outside or in a well ventilated space. I didn't have the luxury but a front-room with a box-fort and windows to blow that air on out so my spacing to spray was limited but good enough.

(One can will do the speaker twice, I of course dicked around and over-sprayed and wasted the can; blame it on the small area to work)

So for each speaker, approximately 2 cans should do the trick for a good seal/prime if I'm not mistaken.

While spraying some gunk landed in the mix, and between that and some excess buildups I had to make corrections before continuing/going to next-coat.

I decided to take a wet sand to it at 220 grit with the sanding block to knock the prime down smooth, seeing how the MDF was now sealed I did the sides too. This noticeable did wonders for both body/face; I was able to get a smooth surface.

Will give this coat time to dry longer, attempted a rush so will need to pay for it, minor set back. I'll have more updates soon.

User avatar
A. Spruce
Posts: 5881
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: MDF - Speaker cabinet damaged - how to properly paint

Post by A. Spruce » Mon Mar 19, 2018 4:19 pm

Good luck, we look forward to your next update. 8-)
If the women don't find you handsome, they should at least find you handy.

CosmosisT
Posts: 27
Joined: Thu Mar 15, 2018 6:13 am

Re: MDF - Speaker cabinet damaged - how to properly paint

Post by CosmosisT » Thu Mar 22, 2018 1:07 pm

Spray painting didn't go as planned, limited space and high VOC. Had some runs here and there. Attempted early sanding (cause the can claimed fast dry times but in the specs hardener takes 1 - 3 days) I wasn't aware and ruined it.

To save myself money as each spray can costed $15, I bought a regular can for $25 at 3x the volume and decided to brush/roll it.

This saved my project and with a final sand it'll smooth things.

I've been using 220 -> 400 grits for sanding primer-coat. Have bee getting good results as long as I wait for the hardener!!!

Should be a few days they can be painted, will likely have to spray unless there's a way I can sand it, and apply a finish.

Post Reply